Synthesis and spectroscopic studies of ( E)- N−-(1-phenylethylidene)nicotinohydrazide (PNH) and some of its metal complexes

Abstract

Four metal complexes with the general formula [M (L) 2(H 2O) x ] (where M = Cu(II), Ni(II), Zn(II) or Co(II); L = ( E)- N − -(1-phenylethylidene)nicotinohydrazide and x = 0 or 2) have been synthesized and characterized using elemental analyses, spectral analyses (IR, UV–vis, MS, 1H-NMR), thermal analyses, conductance and magnetic measurements. The results showed that; 1:2 metal chelates have been formed. The ligand exists in the keto form while it coordinates in the metal complexes in the enol form. Ni(II) and Zn(II) complexes have a tetrahedral geometry, Cu(II) has a square-planar while Co(II) has an octahedral geometry. Semi-empirical calculations (AM1, PM3 and ZINDO/1) have been used to calculate the vibrational spectra with the purpose to facilitate the assignment of the experimental results. Also, optical band gap ( E g) has been calculated to elucidate the conductivity of the isolated complexes. The optical transition is indirect with ( E g) values equal 2.46, 2.58 and 2.56 eV for Co(II), Ni(II) and Cu(II) complexes, respectively.